Police are appealing for witnesses to an horrific road crash in central Queensland yesterday where four people died.

Their car clipped a semitrailer and rolled on the Bruce Highway at Etna Creek, north of Rockhampton, just before 3:00pm (AEST).

A man and woman, both aged in their 50s, a woman aged in her 30s, and another man, all from Sarina in the state's north, died at the scene.

Acting police Inspector Ewan Findlater says it appears the car was trying to overtake the truck as they were both heading towards Rockhampton.

"We will start looking at some physical evidence around the scene ... throughout this section of road and we will try and piece together what has happened," he said.

"There was a couple of witnesses travelling through here at the time of the crash, so we will be speaking to those people and they will be providing us with some valuable information about what has happened here.

"Obviously the Bruce Highway, particularly from Rockhampton to Mackay, is notorious for crashes in the past.

"It's a substantial distance and fatigue becomes an issue and those sorts of things, but at this stage whether fatigue was a factor is too early to tell."